At the peace negotiations of 20 BC, Phraates IV received the concubine Musa as a gift from Rome. He was eventually murdered by Musa and their son, Phraataces. The mother-son conspirators reportedly married and ruled Parthia jointly, as shown on this coin. Horrified Roman sources assert that the pair was killed because of this marriage; however, this was not unusual amongst Parthian Zoroastrians. More likely, Musa and Phraataces were perceived to have lost the khvarnah following territorial losses to Rome.

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